1. Field of the Invention
The present invention relates to a device in a button sewing machine for maintaining looseness in a needle thread while preventing the thread from being pulled out of the eye of the sewing needle.
2. Prior Art
A known button sewing machine is generally composed of a throat plate having a needle threading hole through which a vertically movable needle passes, a feeding plate mounted on the throat plate on which a material to be sewn is placed, and a button holding unit for holding the button and pressing the material to be sewn wherein the button is sewn on the material while the button holding unit moves rightward, leftward and frontward, rearward.
The button sewing machine of this type is fitted with a device to provide appropriate looseness to the thread between the button and the material as well as to retain this looseness and also prevent the needle thread from being pulled out of the eye of the needle. This button sewing machine has a wire made of elastic material which is interposed between the button and the material to be sewn. However, inasmuch as the wire has a base secured to the side of the feeding plate which is not vertically pivotable, the tip end of the wire interposed between the button and the material to be sewn can be pushed upward and warped when the button holding unit is swung upwardly after the button is sewn on the material. When such warping occurs, the wire is plastically deformed and as a result the position of the warped wire must be changed in order to properly interpose between the button and the material. Such change in position reduces the efficiency of the button sewing operation.
More particularly the button sewing machine incorporated a specific mechanism for providing appropriate relative movement after completion of the sewing operation between the wire, button and the material to be sewn, and this mechanism increased the cost and complexity of the machine.